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Subject: [Bug tree-optimization/53773] Vectorizer generates non-canonical multiplies
Date: Tue, 26 Jun 2012 08:31:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53773

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-06-26 08:31:36 UTC ---
Seems this is vect_is_simple_reduction_1's:
      if (check_reduction)
        {
          /* Swap operands (just for simplicity - so that the rest of the code
             can assume that the reduction variable is always the last (second)
             argument).  */
          if (vect_print_dump_info (REPORT_DETAILS))
            report_vect_op (def_stmt,
                            "detected reduction: need to swap operands: ");

          swap_tree_operands (def_stmt, gimple_assign_rhs1_ptr (def_stmt),
                              gimple_assign_rhs2_ptr (def_stmt));
        }

at least on the first testcase.  Now, the question is how hard would it be to
adjust the vectorizer so that it would work even without doing this swapping,
or
alternatively if we shouldn't canonicalize the operand order afterwards.